The joint between the top of a bathtub and the adjacent walls is one of the most pernicious and difficult joints to seal, especially where a shower is installed. The constant exposure to water means that the joint must be absolutely watertight. If water does enter the joint, the lack of air circulation makes it almost inevitable that the underlying walls and adjacent structure will not dry out before the next shower. Structural damage nearly always results, either immediately or over a period of time. The same considerations apply to the joint between a kitchen counter top or sink and the surrounding backsplash. In both situations it is highly desirable to seal the joint completely.
Numerous solutions have been tried to protect the wall from the invasion of water at a joint between the wall and the top of a tub or a counter top or sink. Ceramic tiles with a quarter circle cross section grouted in place have been used. Adhesive products intended to bond yet remain flexible have been tried, and various plastic strips shaped to fit in the juncture of tub or sink and wall or backsplash, respectively, have been tried. Many of these products are difficult for the home owner to install or apply, and others are not entirely effective. That new products continue to appear is ample testimony that the problem has not been completely solved.